Centrifugal-electric clutch



A ril 8, 1952 M. P. WlNTHER CENTRIFUGAL ELECTRIC CLUTCH 4 Sheets-Sheet 1 Filed NOV. '17, 1949 FIG. I.

Pram

Ap 8, 1952 M. P. WINTHER 2,591;989

CENTRIFUGAL ELECTRIC CLUTCH Filed Nov. 17, 1949 4 s he eis-shet 2 O2 F|c;.2.

Ap 8, 1952 M. P. WINTHER CENTRIFUGAL ELECTRQIC CLUTCH Filed Nov. 17, 1949 4 Sh'eet's-Sheet 3 April 1952 M. P. WINTHER 2,591,989

CENTRIFUGAL ELECTRIC CLUTCH Filed Nov. 17, 1949 4 sneak-sheet;

Patented Apr. 8, 1 952 CENTRIFUGAL-ELECTRIC CLUTCH Martin P. Winther, Gates Mills, Ohio, assignor to Martin P; Winther, as trustee Application November 17, 1949, Serial No. 127,898

14 Claims.

'with a modulated action in response to speed of rotation. In an automotive application this allows for preliminary preparation for closure and subsequent actual closure merely by opening the throttle of the prime mover (engine) which drives the clutch. The clutch may subsequently be opened at any prime mover speed.

Some automatic automotive transmissions are designed to employ two rotary power input members which are supplied alternatively with power' from the engine through selectively operable electrically controlled friction clutches. In this connection additional objects of the present invention are the provision of means for alternatively preparing two such clutches for closure from a single exciter coil merely by exciting or deexciting it; the provision of means for modulating the closure of a given prepared clutch in response to centrifugal action as determined by prime mover speed; the provision of means for transferring power transmission from one clutch directly to the other without modulation at a speed above a predetermined value; and the provision of a clutch of the class described which under emergency conditions of current failure of the exciter coil will be in condition for connecting the prime mover with one of said rotary input members to the transmission, so that an automotive vehicle on which the device is located may be brought to a repair point under its own power. Other objects will be in part apparent and in part pointed out hereinafter.

Briefly, the invention in its over-all aspects consists in a compound clutch having a first clutch component and a second clutch component wherein either the first or second component is electromagnetically prepared for closure when the engine is operating at idling speed. The preparation, which is selective, may be simply performed either by exciting or deexciting a magnetic field coil. After either clutch component is prepared for closure, it may ultimately be closed by centrifugal action by operating the prime mover above idling speed. This provides a desirable modulation of closure of the prepared clutch in response to engine acceleration. Moreover, selective alternate closure of the clutch com ponents may be effected above idling speeds without modulation by said excitation or 'deexcitation of the field coil.

In a more specific sense, the invention comprises a toroidal fiux field coil surrounded by magnetizable rings which are axially biased apart by springs but adapted to be attracted against the bias by the magnetic field from said coil only when excited. One of the magnetizable rings when biased (coil unexcited) moves to a position such that it is capable of acting as a clutch-driving element of what will be referred to as a second clutch. On the other hand, when this magnetizable ring is attracted, it influences a second ring to come into position to become capable of acting as a driving clutch element for a first clutch. Thus the potentialities of either clutch to become closed depend upon excitation or nonexcitation of the coil. A third ring is provided for the first clutch and a fourth ring for the second clutch. These are under control of a centrifugal mechanism which in response to increase in speed forces the third and fourth rings toward one another. Stops are arranged for these third and fourth rings such that when the coil is energized, engagement of the fourth ring with its stops provides a fulcrum for drawing the third ring (short of its stops) to squeeze a driven clutch disc of the first clutch. When the coil is deenergized, the said second ring ceases to provide any reaction and the first clutch opens, whereupon the third ring engages its stops and thereafter provides a reaction whereby the fourth ring under centrifugal action may be forced toward (but short of) its stops. At this time the first magnetizable ring, bein released against its stops, is in the position to provide reaction so that the centrifugal mechanism can squeeze a driven element of the second clutch against the first ringto close said second clutch.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of th application of which will be indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

Fig. 1 is a longitudinal section of a compound clutch embodying the invention, prepared for closing its first clutch component, being taken on line II of Fig. 3;

line 2-2 of Fig. 3;

Fig. 3 is a cross-sectional view of the right end of the device, taken on line 33 of Fig. 1 but on a reduced scale;

Fig. 4 is a fragmentary view similar to the upper portions of Fig. l but prepared for closing the second clutch component.

Fig. 5 is a side elevation of a detached centrifugally operating weight lever; and

Fig. 6*is a plan view of Fig; 5; being an inside view of the lever when in position in the clutch.

Similar reference characters indicate corresponding parts throughout the several views of the drawings. I

Referringnow more particularly to Fig. 1, there is shown at numeral I aidriving hub'which is adapted to be fastened to the driving flange of a prime mover such as an automotive; engine, fasteners 3 being indicated for the purpose. A

rotary clutch housing or driver is indicatedLin general at numeral 5, a front plate I of which is. attached to the hub I. the usual prime mover starter gear 9 and an attached ring II. Bolted to the ring- II is a rear. cover I3 which carries a'sleeve I5-supported inisuitable bearings I'I within a part of the sup porting frame I9. Bolts for fastening the cover I3. are shown at 2I. Only asmall partof the frame I9 isshown, sinceit may constitute any suitable part, .such'as the front end of an automatic or other transmission to which the clutch isattached. The members I, II, I3 and I5.- rotate as a unit, being driven from the prime'mover.

Attached by means; of. bolts- 23- to and rotarywith. ring I I isanaxially fixed magnetizable: ring 25. This. ring isrecessed. to accept an annular. field coil 21. The coil 2:! is-excited through a circuit including wires 29 which lead to a slip ring 31 carried on the sleeve I5: but insulated therefrom by a band of insulation 33. The-circuitv isclosed through a brush 35'. The coil 21- is grounded through the rotating parts abovementioned, including the sleeve I5, the grounding connections'being completed through an addi--' tional slip ring 31 in connection with which a brush 3'9-is used. Further circuit details for exciting coil 2'I are-unnecessary, such being well known'in'this art.

The magnetizable ring 25 carries permanently inserted studs M which extend out on both sides ofit: On' the right side, the extensions areindicated by numerals 43. elude permanently attached shoulder-forming sleevesv The shoulders 45* are located in openings.53 of a first backing ring- 41 which may slide axially on said shoulders.

openings 5| for the: purpose; tween. the rings 41 and 49'is' a first clutch disc 55, provided with frictionfacing SI. This? clutch:

disc has a central hub 59 slidingly splined atBI to: avquill or first driven member 63 which forms one of "the power input'members for.th'e,transmis'-.-

sion-whiclrthe. clutch serves; Thus-disc 'has afloatinglocation between rings 41 and. A

hearing 65 is" interposed. between quill- 83. and

sleeve: I52 133; means ofthe spline BI the hub 59iisif'ree to floataxially on theiquill 63 but r0- tates therewith, forming a drivingconnection.

' Theipins 4I also have extensions 51 from the left side of thering 25; upon which are shoul ders=69-. Within the shoulders 69-and'carried upon the inner portions of extensions 6-! (by means: of openings-'11) is a magnetizable ring 13. The shoulders 69 are so positionedthat the This plate I carries The extensions 43 in-- The extensions 43 beyond the. shoulders 45 slidably'support aflrst' pressure': ring 49; passing through. suitable Sandwiched b8l-- 4 ring I3 may move axially. Inner spacing pillars I5 extend from the plate 41 (above described) into abutting engagements with seats I1 in the ring I3. The pillars I5 pass through pockets I9 in the ring 25. In the pockets are also compression rings 8|. For balanced guiding action, additional outer pillars 16 are employed (Fig. 2). They also extend from the ring 41 loosely through openings Ill in the ring 25 and into outer seats I4 in thering I3. Thus the rings 41 and I3 may approach one another only a predetermined amount. In order to complement the springs SI (for balanced action), there are provided separating compression springs 82 in pockets of the ring; 25 which also react against the ring I3 (see Fig. 2). These springs 82, in addition to springsw BI, tend to bias apart the rings 25 and I3.

The outer ends of the left-hand extensions 61 passsinto openings 83 in lugs 84 of a pressure ring 85. Between this ring 85 and magnetizable ring I3. is a second clutch disc 81, provided with friction facing 89. The disc 81 has a central hub 9 I, slidingly splined as shown at 93 to a shaft 95, the latter constituting the second power input member to the transmission served by the apparatus. Thus disc 81 has a floating location between rings 85 and 13. The splines 93 permit axial play but effect a rotary driving connection.

The shaft 95. is carried within a pilot bearing S'Isupported in the main hub I. The connection between the clutch disc 81 and-the hub 9| is through a spring vibration damper arrangement shown at 99, further description of which will not be necessary, sincesuch an arrangement is a refinement and common between clutch discs and their. hubs. A similar. arrangement. is not required-for the clutch disc 55 (rivets 56 being used) because.- the characteristics of the transmission-served by this. apparatus require torsional vibration damping. only inconnection with the disc 81.

To the left of the extensions 6.! is a reaction ring- IOI which is connected with ring 49 through tension rods I03 having heads I05. Beneath the heads I05 are compression springs I01 which are carried in and seat within pockets I09 formed with the ring 49. The tendency of the springs I01 is to bias together the rings 49 and IN. Within the ring MI is a heel seat II I and on the outside of the ring 85 is a toe seat II3. At

I I5. are shown centrifugal weight levers (see Figs. 5 and 6-). Each weight lever II5 is constituted by a central weight-forming portion N1, the contour of which is such as to clear the rods I03, pockets I09'and other parts. The rings 25 and 1-3 are suitably notched as shown at H9 and I2I to. accommodate thiscentral. mass Ill. Each lever has a foot II8 incorporatinga heel I23 hearing within the seat III of ring IOI and a toe I25 bearing upon the seat II3 of the ring 85. In view of the tendency of springs I0'I to bias together the rings 49 and IM and the action of the. heels I23and toes I25 on rings IOI and 85, respectively, the lever weights II5 are normally biased to a counterclockwise position (referring to Fig. 1). The reactionpoints required for this actionwill be. discussed below. Under centrifugal forceinduced by rotation, the leverweights II5 tend to move in a clockwise direction.

As shown in Fig. 2, the rings 85 and MI are resiliently biased together by studs I21 attached to lugs I02 on ring IM and passing through openings I29 in lugs I3Iextending from the ring 85. These'studs I2'I carry heads I33 underneath which are springs I35 which react against the ilugs" I 3| of ring 85. Suitable pockets I31 are arranged in rings 13 and 25 to accommodate the studs and springs where peripherally located.

The sections shown in Figs. land 2 have been selected to show one each of various identical multiple elements. As appears, in Fig. 3 there are in fact spaced at equal intervals three studs 4|; three pockets 19, studs 15" and springs BI; three studs 16, pockets 80 and springs 82; three studs I21. heads I33 and springs'I35; and six pockets I09, rods I03, heads I05and springs I01.

In order to provide desired'time' delay for any approach of rings 13 and 85', the latter (Fig. 2) is provided with lugs I39. There are provided oppositely at intervals around the ring 13 circular pockets I4I, each covered "by 'a resilient diaphragm I43. Each pocket I4I is'connected with an inwardly located circular fpocket I45 by means of a restrictive port I 41. Pocket I45 is enclosed by a cover I49. A suitable fluid, such as'a con stant viscosity oil, fills the pockets I 4|. Under rotation such oil tends to spin out into pockets I4I. Upon any relative approach between rings 13 and 85, the lugs I39 compress the diaphragms I43, thus forcing the fluid out 'of pockets I4I into pockets I 45 through the restricted passages I 41, thus providing a time delay for said approach. When rings 13 and 85 are permitted to separate, the fluid then in the inner pockets I45 moves by centrifugal forc outward into pockets I4I via the passages I41, ready to be squeezed in again upon the next approach cycle. It will be understood that only one time-delay system involving pockets I M and I45 is shown in Fig. 2 but that three of these are employed at equally spaced intervals around the peripheryof the device, the others being out of the plane .of the section of Fig. 2 and not dotted in Fig. 3.

Operation is as follows:

Assume that coil 21 is excited and the engine to be operating within idling range (say at 500 R. P. M.). This rotates the clutch housing 5, including covers 1 and I 3,'rings II, 25, 41 and 49 (which form the driving members of what will be referred to as clutch -1); and rings 13, 85 (which form the driving members of what will be referred to as clutch C-Z) .Under idling conditions (speeds under a predetermined amount) and the coil 21 excited, the parts are in the Fig. 1 condition (weights II in)"wherein the spacing between rings 41 and 49 andthat between rings 13 and 85 is sufficient that'no frictional drive is deliveredto either disc 550i clutch C-I or disc 81 of clutch 0-2. But excitation has prepared clutch C-I for closure since the flux field of the coil 21 has attracted the ring 13 so that rings 25 and 13 are as close together as they can be. Ring 13 opens free space for disc 01. At this time springs BI and 82 are compressed. The seats 11 and 14 in ring 13, through pillars 15 and 16, transmit motion to the ring 41 so that it is as far to the right as possible. This pushes the outer face of lining 51 beyond stops 45. Under idling conditions, the centrifugal force is insumcient to throw the weights I I5 enough clockwise substantially to compress springs I01 (through any levering action of the heels-123 and toes I25 on the seats I I I and I I3, respectively). Thus ring 49 opens free space for disc 55.? However, when the speed is increased above idling (above a speed predetermined by a setting of-heads I05 or I33 in connection with springs I01 or I35, respectively), the lever weights- II5. move outward (clockwise, Fig. 1). The result is that feet II8 are turned clockwise. Heels I23 move to the left,

to springs I01, which push resiliently on ring 49,

moving it to the left. Since the clutch disc 55 (including its lining) is now backed by the magnetically held ring .41 in its right-hand position, the clutch disc is squeezed by rings 41 and 49. The squeezing force increases with increase in speed, springs I01 deflecting increasingly. Upon a suilicient increment of speed increase, clutch C-I after an initial period of slip under acceleration becomes locked shut in synchronism between its driving and driven elements. At this time the ring 49 does not reach the shoulders 45. Thus clutch C-I is modulated shut while clutch 04' remains open at speeds above idling.

If at said speeds above idling it is desired to open clutch C-I and close clutch C-2, it is'only necessary to deexcite coil 21. Springs 8| and 82 will then bias the ring 13 leftward into engagement with the clutch disc 81, which is backed up by the ring 85. Note that stops 69 are narrower than the thickness of disc 81 and its lining. The action for holding ring is supplied by the centrifugal force of weights II5, which rock on the heels I23 and bias ring 85 to the right by means of the toes I25. The reaction for this condition is furnished through the rods I03, springs I01 and ring 49, which seats on the shoulders 45. Note that the length of stops 45 is more than the combined thicknesses of ring 41 and disc 55 with its facings. Hence clutch C-I cannot close. Should the speed of the clutch decrease below the predetermined setting for centrifugally holding either clutch shut, both clutches will be open, regardless of whether or not the coil 21 is excited or deexcited.

From the above it will be seen that any transmission served by the present clutch depends for any completely automatic electrical operation upon current being available for the coil 21. It sometimes happens that a vehicle has a dead battery, in which event it is desirable to be able to drive it under its own power to a repair point. This is possible with the present clutch because when coil 21 is deexcited (dead battery), clutch C-2, although open under idling conditions, is in efiect prepared for subsequent closure when the engine is accelerated above idling speed (see Fig. 4). This is because the ring 13 is then biased against the stops 69 by springs 8| and 82. At idling speed the ring 85 will float to the left (weights II5 inward). However, when rotation is increased above idling speed, the weights II5 move outward, turning the feet II8 clockwise to force ring 85 to close against the disc 81 which is backed by spring pressed ring 13 now acting as a backstop. Reaction is provided through rods I03 and springs I01 from the ring 49, which willythen be on the shoulder stops 45, clutch C-I remaining open.

Among the advantages, in addition to those already'made clear from the above, is the fact that all clutch-closing forces are applied through springs, which with the modulating centrifugal closing action and the time-delay action furnished by the hydraulic elements I4I, I43 and I45, assures smoothly modulated clutch closures with smooth accelerations.

Terms used in the following claims have for escapee the most part been definitively described above.

'The term centrifugal mechanism will :be understood to refer "to the lever weights II5 with the In addition, for brevity, ring :41 is referred to as a first backing'ring, rin I3 as a second back- .ing .ring, ring 49 as a firstpressure ring and .ring 85 as a second pressure ring. Stops 45 .are referred to as a first set of such zmembers, operative in cooperation with the first .rings 41 and49 .in the first clutch C-I. Stops'69 are referred to as a second set of suchstops, operative in-cooperation with the second rings I3 and 85 in the second aclutch -2. It will .bQIlOtGd that each of the backing "rings '41 and I3 in its position farthest away from the coil.2 I holds its respective Ilriven disc .55 or 8.1 in a position where the respective pressure ring 49 or 85 can press the respective floating disc 55 or '81, since these pressure rings cannotthen reach :their stops. Otherwise they can, .but under the latter conditions the backing rings cease to provide any reaction for clutch closing. In the case .of the backing ring 41, electromagnetic means (excitation of coil 21) results in the backing ring 4! assuming its position preparatory to centrifugal clutch closing by ring '49. In'the case of the backing ring I3, spring pressure means (springs 8I and .82 in :the absence of excitation of the coil 21) cause the backing ring 13 to assume its position preparatory to centrifugal clutch closing by ring 85. Heads I05 constitute means for adjusting the speed at which the centrifugal mechanism can be adjustedhto respond'toa desired speed.

The expansible chambers 141, 'with chambers I45 and throttles I'4I, constitute a time-delay mechanism operative in association with the centrifugal mechanism for delaying clutch closure. It will be observed that this time-delay mechanism is effective :in connection with both clutches C-I and 0-2 because it is within the train of force reactions during either clutch closure. The train of force reactions is as follows. After C-I is prepared for engagement (at idling speeds and by exciting coil 21.) the movement of weights 'II 5 (with corresponding movement of shoes H8) in response to :the increasing speed of the prime mover causes rings MI and 85 to be moved away from each other relatively, and against the "bias of springs I35. Ring 85 is thereby forced to the right toward stops 59and ring I3, and its points of reaction are initially against the diaphragms I43. .As the movement of ring 85 is cushioned by diaphragms I43, ring IOI will be moved to the left away :from ring 85 and draw with it'ring 49 against the biasing action of springs I01. In this way there .is a time delay effected in the closure of C-I. As to delay in closing 0-2 from a start, coil 21 being deenergized and ring I3 being to the left, the engagement of 0-2 is de- 'layed by the squeezing of diaphragms I43 against lugs I39 of ring 85. It will be understood that after a start has been accomplished by closure of clutch 'CI with time delay (ring 85 seating on the stops 69 and weights III out) there will also be time delay in closing clutch 0-2 when coil 2! is deenergized under running conditions, for this releases ring I3 for movement to the left. In this event the expanded diaphragms I43 carried on ring I3 will engage lugs I39 of ring 85, thus introducing the delay. This delay mechanism is effective regardless of the adjustments of heads I05 for clutch closure speed response.

In view of the above, it will be seen that the several objects :of theinvention are achieved and -'other advantageous results attained.

Asimanychanges could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted 'as illustrative and not :in a limiting sense.

I claim:

1. A clutch comprising a driver and a driven membenamagnetic field member rotary with the driver, an axially movable backing ring also rotary withthe driver, means for moving the backing ring from a first to a second position in response to excitation of the field member, an axially movable -pressure ring rotary with the driver, a driven disc rotary with the driven member and-having a floating location between said rings, a centrifugal mechanism responsive to rotation of the driver adapted to move the pressure ring toward the backing ring in response to a predetermined speed, and stops so arranged that when the field member is excited the pressure ring in response to said centrifugal mechanism can :press the driven disc against the backing .ring in :its 'second position, and when the field .member is deexcited the pressure ring will engage the :stops and the backing ring may move into its first position 'wherein the driven disc is released.

'2. A clutch made in accordance with claim 1, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed.

3. A clutch 'madein accordance with claim 1, wherein a time-#de'lay mechanism is operative in connection with the centrifugal mechanism adapted to delay clutch closure by delaying movement of the pressure ring as it moves toward :the'backing ring.

4. A clutch made in accordance with claim 1, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed, and wherein a timedelay mechanism is operative in connection with the centrifugal mechanism adapted to delay clutch closure regardless of the adjustment of said adjusting means.

5. A clutch comprising a driver and a driven member, :a magnetic field member rotary with the driver, :an axially movable backing ring also rotary with the driver, means for moving the backing ring from a first to a second position in response to deexcitation of the field member, an axially movable pressure ring rotary with the :driver, a driven disc rotary'with the driven member and having a floating location between said rings, a centrifugal mechanism responsive to rotation of the driver adapted to move the pressure ring toward the backing ring in response to a predetermined speed, and stops so arranged that when the field member is deexcited the pressure ring in response to said centrifugal mechanismcan press the driven disc against the backingringiniits second position, and when the field member is excited the pressure ring will engage the stops and the backing ring will move into its first position wherein the driven disc is released.

6. A clutch made in accordance with claim 5, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed.

7.. A clutch made in accordance with claim 5, wherein a time-delay mechanism is operative in connection with the centrifugal mechanism ment of the pressure ring as it moves toward the backing ring.

8. A clutch made in accordance with calim 5, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed, and wherein a time-delay mechanism is operative in connection with the centrifugal mechanism adapted to delay clutch closure regardless of the adjustment of said adjusting means.

9. A clutch comprising a driver, first and second driven members, a magnetic field member rotary with the driver, first and second axially movable backing rings both rotary with the driver, means for moving the first backing ring from a first to a second position when the field coil is excited, means for moving the second backing ring from a, first to a second position when the field coil is deexcited, first and second axially movable pressure rings rotary with the driver, a first driven disc rotary with the first driven member and having a floating location between said first backing and pressure rings, a second driven disc rotary with the second driven member and having a floating location between said second backing and pressure rings; a centrifugal mechanism responsive to rotation of the driver adapted to move the first and second pressure rings toward the first and second backing rings respectively in response to a predetermined speed; first stop means so arranged with respect to the first pressure and backing rings that when the field member is excited the first pressure ring in response to said centrifugal mechanism will clamp the first driven disc against the first backing ring in its second position, and when the field member is deexcited the first pres sure ring will engage the first stop means and the first backing ring will move into its first position wherein the first driven disc is released; and second stop means so arranged with respect to the second pressure and backing rings that when the field member is deexcited the second pressure ring in response to said centrifugal mechanism will clamp the second driven disc against the second backing ring in its second position, and when the field member is excited the second backing ring will disengage the second stop means and move into its first position wherein the second driven disc is released.

10. A clutch made according to claim 9, wherein a time-delay mechanism is provided in association with the centrifugal mechanism adapted to delay the movement of either pressure ring as it moves toward its respective backingring.

11. A clutch made in accordance with claim 9, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed.

12. A clutch made in accordance with claim 9, wherein an adjusting means is provided in connection with the centrifugal mechanism for predetermining said speed, and wherein a timedelay mechanism is provided in connection with the centrifugal mechanism adapted to delay clutch closure by delaying movement of either pressure ring irrespective of the adjustment of said adjusting means.

13. A clutch comprising a, driving member, a driven member, a backing ring rotary with the driving member, an axially movable pressure ring rotary with the driving member, a driven disc between the backing and pressure rings and attached to the driven member, a speed-responsive centrifugal mechanism adapted to move the pressure ring toward the backing ring to engage the driven disc for clutch closure, and a time-delay mechanism for delaying action of the centrifugal mechanism, said time-delay mechanism comprising an expansible chamber on a relatively larger radius and containing a fluid, and a receiving chamber on a relatively smaller radius in restricted communication with the expansible chamber and adapted to receive fluid therefrom, both chambers being on one of the members rotary with the driving member, an expansible part of said expansible chamber being engageable by a part on the pressure ring for movement of fluid toward the receiving chamber when the pressure ring moves toward the backing ring, centrifugal force returning fluid from the receiving chamber to the expansible chamber upon recession of the pressure ring away from the backing ring.

14. A clutch comprising driving and driven members, a driven disc on the driven member and relatively axially movable rings on the driving member for clamping said driven disc and adapted to move toward and away from one another, a time-delay mechanism for delaying clamping action comprising an expansible chamber on a relatively larger radius in one of the relatively axially movable rings and containing a liquid, a receiving chamber in the last-named ring on a relatively smaller radius in restricted communication with the expansible chamber and adapted to receive liquid therefrom, an expansible part of said expansible chamber being engageable by a part on the pressure ring for movement of liquid toward the receiving chamber when the pressure rings approach one another, centrifugal force returning liquid from the receiving chamber to the expansible chamber when the pressure rings separate.

MARTIN P. WINTHER.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS 

